Five members of a family were burnt in a septic tank blast at their Dakshin Khan house of Dhaka early today.

The victims are Rumana Akter, 30, her seven-year-old daughter Monika Akter, brother Imran Hossain, 27, and his wife Jannat, 20, and their two-year-old daughter Tasfia.

They are undergoing treatment at the burn unit of Dhaka Medical College and Hospital where condition of Rumana is said to be critical as she suffered 60 percent burn injuries, DMCH sources said.

The incident took place at their one-storey building in Fayedabad area around 5:30am, said Hedayet Hossain, a sub-inspector of Dakshin Khan Police Station.

Police suspect that the explosion occurred when toxic gas of a septic tank came in contact with electricity, the SI said.

Some furniture and many other valuables of the house were also damaged in the blast, police said.